I wouldnt worry about being the only one to feel like that as it is perfectly normal. I have just gotten back from 6 months teaching english in Japan, and when i first got there i felt terrible. However, when i left, i was sad to leave. I will be coming to the south of france on Oct 5th, and will be kinda near you! I have just looked on multi map and it reckons the places we are staying are about 1hr 30 away by car. I have access to a car, and have saturday afternoons and sundays off, and would love to meet up and have a chat, and hopefully get to know you. As i said, ill be in france in a couple of weeks, so drop me an email if youd like to meet at some point and we can make some arrangements.
Do you speak French? I imagine it would be harder if you didnt, but if you do, it would be a good opportunity to practice by making friends.
Must dash, only go 2 weeks in UK before heading off to france, and got soooo much to do! Just persevere with the au pairing, and it will get better.